This invention relates to forms for concrete and the like and more particularly to an improved unitary article of manufacture for use in assembling such forms in the field.
In constructing walls, foundations, curbs and the like of concrete or similar initially fluid materials which subsequently harden into the desired structure, it is common to fabricate a form consisting of spaced sides or panels defining the exterior side surfaces of the desired structure. It has been proposed in the prior art to provide elongated metal members or form ties adapted to extend between the sides or panels of a form and temporarily tie the sides or panels of the form to each other while concrete, for example, is poured into the form and allowed to harden. Such form ties are thus embedded in the concrete and means are provided for the subsequent release of the form sides from the form ties so that the form sides or panels may be removed for reuse.
U.S. Pat. Nos. 1,097,796 (Fuehrer) and 1,729,807 (Toogood) are representative of prior art form ties. However, the form tie disclosed by Fuehrer will not resist either shear forces or transverse forces acting on the form sides unless used in pairs at given locations to form an X-shape configuration. The form tie disclosed by Toogood will resist transverse forces acting on the form sides when used alone at a given location but will not resist shear forces even if more than one is used at a given location.
It is an object of this invention to provide a unitary form tie which will resist both shear and transverse forces acting on the form sides at a given location when used by itself at such given location.
U.S. Pat. No. 3,199,827 (Terry) discloses a preassembled multi-element form tie which includes a pair of elements similar to the form tie described by Toogood interconnected by additional elements adapted to resist vertical shear forces. However, the form tie disclosed by Terry is not as effective as a pair of form ties as disclosed by Fuehrer of comparable size in resisting vertical shear forces even though it is more complicated in structure.
It is an object of this invention to provide a unitary form tie which will provide resistance to vertical shear forces acting on the form sides at a given location approaching maximum for its size when used by itself at such given location.
It will be noted that none of the form ties of the prior art provide resistance to horizontal shear forces acting on the form sides.
It is an object of this invention to provide a unitary form tie which may be oriented to resist horizontal shear forces acting on the form sides in addition to resisting vertical shear forces and transverse forces acting on the form sides.